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Unconnected pins
Alternate Port
Functions
2467S–AVR–07/09
If some pins are unused, it is recommended to ensure that these pins have a defined level. Even
though most of the digital inputs are disabled in the deep sleep modes as described above, float-
ing inputs should be avoided to reduce current consumption in all other modes where the digital
inputs are enabled (Reset, Active mode and Idle mode).
The simplest method to ensure a defined level of an unused pin, is to enable the internal pull-up.
In this case, the pull-up will be disabled during reset. If low power consumption during reset is
important, it is recommended to use an external pull-up or pull-down. Connecting unused pins
directly to V
or GND is not recommended, since this may cause excessive currents if the pin is
CC
accidentally configured as an output.
Most port pins have alternate functions in addition to being general digital I/Os.
how the port pin control signals from the simplified
functions. The overriding signals may not be present in all port pins, but the figure serves as a
generic description applicable to all port pins in the AVR microcontroller family.
Figure 33. Alternate Port Functions
Pxn
PUOExn:
Pxn PULL-UP OVERRIDE ENABLE
PUOVxn:
Pxn PULL-UP OVERRIDE VALUE
DDOExn:
Pxn DATA DIRECTION OVERRIDE ENABLE
DDOVxn:
Pxn DATA DIRECTION OVERRIDE VALUE
PVOExn:
Pxn PORT VALUE OVERRIDE ENABLE
PVOVxn:
Pxn PORT VALUE OVERRIDE VALUE
DIEOExn: Pxn DIGITAL INPUT-ENABLE OVERRIDE ENABLE
DIEOVxn: Pxn DIGITAL INPUT-ENABLE OVERRIDE VALUE
SLEEP:
SLEEP CONTROL
Note:
1. WPx, WDx, RLx, RPx, and RDx are common to all pins within the same port. clk
and PUD are common to all ports. All other signals are unique for each pin.
Figure 30
(1)
PUOExn
PUOVxn
1
0
DDOExn
DDOVxn
1
0
PVOExn
PVOVxn
1
0
DIEOExn
DIEOVxn
1
SLEEP
0
SYNCHRONIZER
SET
D
D
Q
PINxn
L
Q
CLR
PUD:
PULLUP DISABLE
WDx:
WRITE DDRx
RDx:
READ DDRx
RRx:
READ PORTx REGISTER
WPx:
WRITE PORTx
RPx:
READ PORTx PIN
clk
:
I/O CLOCK
I/O
DIxn:
DIGITAL INPUT PIN n ON PORTx
AIOxn:
ANALOG INPUT/OUTPUT PIN n ON PORTx
ATmega128
Figure 33
can be overridden by alternate
PUD
Q
D
DDxn
Q
CLR
WDx
RESET
RDx
Q
D
PORTxn
Q
CLR
WPx
RESET
RRx
RPx
Q
Q
CLR
clk
I/O
DIxn
AIOxn
shows
, SLEEP,
I/O
71
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